Direct-drive linear machines have been used more frequently in several areas, including in industrial applications. Recent trends have led to such machines being used in place of more traditional hydraulic, pneumatic, or geared electric actuators when linear motion is desired. Typical linear motors have the magnets in the translator and the windings in the stator or vice versa. For long-stroke applications, these drives become very expensive.
In addition, existing linear machines exhibit poor performance operating under fault conditions, poor thrust versus current linearity characteristics, high detent force, and high saturation effect on thrust. Magnets can also be de-magnetized due to the current in the windings.